A wide variety of building and similar projects require preparatory work such as leveling, grading and filling of underlying soil, gravel or other materials. Highway and building construction, for example, typically requires that a prepared bed of compacted work material be provided upon which pavement, concrete, etc. is to be laid. In some instances, material fill for such purposes must be brought to the work site from another location. In others, material must be removed or redistributed. Foundations for buildings, dams, airports, factories and other construction projects generally present similar issues relating to elevation profile, slope, proper work material type, etc. Virtually all civil, environmental and other construction endeavors require at least some work material transport, and it will thus be readily apparent that the capacity to move relatively large quantities of material in an efficient manner may be paramount for the success of many public and private works projects.
To move relatively large volumes of material, construction contractors often utilize machines known as “scrapers” to remove material from one location and transport it to another. The term “scraper” generally refers to the ability of the machine to remove an overlying layer of work material from a work surface. Typical machines employ a scraper blade or cutting edge which may be moved through work material beneath the machine to remove a top layer of material. The removed material is placed into a “bowl” of the scraper, then transported to a different work site or different area of a work site for deposition. Efficient loading and unloading of the bowl in scraper machines has long presented an engineering challenge.
Certain scraper machines, known in the art as open bowl scrapers, rely upon forward motion of the machine to urge work material removed with the scraper blade backward and upward into the bowl. This approach generally requires a relatively large and heavy machine to provide sufficient power for driving the machine, removing material, and filling the bowl of the scraper. The challenge is compounded by traction losses of the machine during such operation. In some instances, separate tractor machines are used to push or pull self-propelled and other types of scrapers to enhance their ability to load a desired volume of work material.
Engineers have developed certain strategies addressing the loading and unloading challenges experienced with traditional open bowl scrapers. In one design, an elevator apparatus having paddles is used to lift work material from the vicinity of the scraper blade upward, thenceforth dumping the material into the bowl. Elevator designs have met with significant success, however, the relatively large number of moving parts and overall complexity of the apparatus tends to result in high wear and significant maintenance issues. Elevator scrapers also tend to generate significant dust.
Another strategy employs one or more augers within the scraper bowl to distribute the work material after it enters the bowl in a more even fashion than that achieved with a conventional open bowl design. In such bowl and auger systems, rotation of a load-distributing auger can lift work material within the bowl and urge work material toward the sides of the bowl such that the scraper machine may more easily push additional work material into the bowl via its forward travel. While systems employing load-distributing augers have various advantages, including some conditioning and mixing of the work material, the auger tends to take up significant space within the volume of the bowl, limiting the carrying capacity of a scraper machine of a given size. Moreover, ejection of material from the bowl tends to be problematic as it must generally be moved around the auger. The ejector system itself can occupy a significant amount of bowl volume.
One example of a scraper machine having a load distributing auger is known from U.S. Pat. No. 3,533,174 to Carston. In Carston's design, an auger is positioned within the bowl of a scraper machine at a generally vertical orientation. The auger receives loosened material within the bowl from a cutting blade as the machine is moved forward. While Carston's strategy, provides certain advantages over open bowl scrapers, the design is subject to the same limitations mentioned above with respect to the bowl capacity. In other words, Carston' auger takes up a substantial amount of bowl volume that might otherwise be available for carrying work material. Thus, certain of Carston's potential advantages are at least somewhat overshadowed by the loss in work efficiency. Moreover, because of the auger's position, the machine still relies largely upon forward travel to push material into the bowl.
The present disclosure is directed to one or more of the problems or shortcomings set forth above.